Method of producing carbon and such carbon



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Filed Aug. 2, 192s c. B EDWARDS ET AL 51M v s A METHOD OF PRODUCING CARBONv AND SUCH CARBON Jan. 20, 1931.

ne. lA TORNEYS.

Patented Jan; 20, 1931' UNITED STATES PATENT oFFlcE CARLETON B. EDWARDS AND HAROLD R. .HORNER, OF INDIANAPOLIS, INDIANA, AS-

. SIGNORE -TO PETER C. REILLY, OF INDIANAPOLIS, INDIANA Application med August a, 192s. serial ma 126,569.

This invention pertains to a method of producing carbon and to the carbon as a new article of manufacture, the carbon possessing certain peculiar and highly valuable characteristics as will hereinafter appear in detail.

Broadly stated, the method consists in calcining pitch coke and thereby converting the same into a substantially pure carbon especially adapted for the production of electrodes. The coke employed may be derived from various sources but more particularly we propose to employ coke produced from coal tar, or coal tar pitch, or petroleum coke. Preferably, we em loy the former as the starting material. uch coke is set forth and claimed in U. S. Letters Patent to Reilly No. 1,230,782, dated June 20, 1917, and for the purposes of description will hereinafter be referred to as Reill coke. Said Reilly coke is characterized by ing dry and sponge-like in appearance, amorphous, presenting, when fractured, a steel-gray surface with a brilliant, glossy surface upon the-walls of the depressions or recesses appearing therein. This coke is anon-conductor of electricity as is also the petroleum coke, but by the process hereinafter set forth, such cokes are S0 changed as to produce a carbon having a high degree of electrical conductivity and, as a consequence, well adapted for the manufacl y ture of electrodes.

In carrying out our process we employa suitable retort and in the annexed drawings there is shown one embodiment wherein our process ma Vbe effectuated.

In said rawings':

Figure 1 is a vertical sectional view of the retort,

Figure 2 a similar view taken on the line II-II of Figure 1, and

Figure 3 a horizontal sectional view taken on the line III-III of Figure 1.

The body of the retort denoted by 1 is Abuilt up of suitable refractory and, from the base or foundation 2,' is of a height of approximately twenty-two feet;

` The interior of the retort is preferably of the same 'dimensions throughout and, with a view of securing uniform roduction, is made substantially oblong or e 'ptical in cross section ;-this for the reason that it is necessary to effect the same reaction throughout the entire mass as it passes down vthrough the retort.

Where the mass isv of a cross section'too great to permit the indrawn air to penetrate the same, unsatisfactory results obtain.

It is, of course,`apparent that a retort circular in cross section, where the diameter is small enough, could be employed with, however, a reduction in the bulk of material treated.

The upper end one or more gas off-take pipes 4 and 5 which pipes are connected with suitable exhausters' (notshown).

yA feed pipe 6 is also Supported by the top 3 and is surmounted by a-hopper 7 with which is associated a sealing feeding -valve 8 of conventional form.

Located at the lower end of the retort chamber is a series of conveyor screws 9, said screws extending outwardly into housings 10 each of which is provided with a of the retort is provided 'with a suitable top 3 through which extend Opening through the wall of the retort u on a line between say eight and ten feet above the base, is a series of air inlet openings 15 and through which air is drawn inwardly to support the combustion of the coke as it passes downwardly from the upper end of the retort.

In operation, the coke, in lump 4form and' of the character set forth, is charged into the retort and suction established through the off-takes 4 and 5, valves 12 at such time being closed.

Initial ,ignition ma be effected in `any approved manner, an once ignition is hadl` 30 v pieces of carbon immediately be 'n to cool lines 4 and 5. 'The coke as it passes down-v and the requisite temperature is reached, the process becomes a continuous one.

The coke passes slowly down through the retort in counter-current to the hot gases passing up from the combustion zone designated by A and out throughthe exhaust wardlyfthrough the retort is subjected to increasing temperature at the rate of approximately 160 C. per foot of distance of fall from the upper end of the retort to the combustion zone.

At the lower temperatures the moisture is driven olf. When 450 C. is reached de'- composition of the hydrocarbons remainin in the coke occurs and this; continues stea ily until the coke reaches the combustion zone where oxygen from the air entering the air holes 15 burns around the surface of each piece,I raisin it to the maximum temperature obtaina le in such internal combustion arrangement. The temperature obtaining in the combustion zone is from' 1600 C. to 1930 C. and this intense heat decomposes the last portion of the hydrocarbons and produces a carbon approaching graphite in purity, electrical conductivity,

specific gravity, and likewise diiiicult toigmte. After passing the combustion zone the and no further loss is sustaine In .the lower portion of the retort, or that marked B, the carbon is gradually cooled and is continuously removedby the conveyers 9 or any equivalent means.'

A s before noted, he raw coke is continuously fed into the upper end of the retort by the valve 8. The gas enerated in the combustion zone A 1s rawn upwardly through the suction ap lied to the outlet pipes 4 and 5 and steadily drops from its maximum temperature as it passes upward- 1y in counter-current to the down coming coke.v In its passage up through the charge, the gas loses its heat until it is removed,

the temperature atsuch time approximating 150 C. Thus a very eiiicient heat exchange is obtained and a very great fuel economy results. The'gas which is drawn off is avery satisfactory type of producer `gas and is utilized for generating power for operation of the mechanical elements associated with the retort and' may be used for other purposes as well.

As above noted, he retort must necessarily be rather narrow in cross section, not

exceeding twenty-four inches in diameter if the retort is circular, or not more than twenty-four inches across if the retort is of the form shown in the drawings. This is necessary in order that combustion be obftained 'around every piece of coke or carbon and is seemingly the .only way of obtaining factured from carbon a perfectly uniform product and the greatest economy in carbon consumption. i

The carbon produced by the method above outlined is especially adapted for the production of electrodes. Electrodes manu- (produced by the above method are burne with greatl diiliculty and are superior to ordinary electrodes and have a relativel long life.

The various properties, c emical and physical, which clearly distin 'sh the present carbon from others, when illy coke is employed as the starting material, are asfolows: Y. l

' Uharacterz'stcs v1. Apparentdensity of size .375 to In addition to the foregoing, the highest grade electrode carbon we have been able to produce has the following characteristics:

Moisture None Volatile None Ash .12%

Electrical resistance- .05 ohms (per hnear inch of a one inch dipressure of 150 lbs. per s inch. Size of car on-- to 65 mesh) Fixed carbon 99.6%

Specific gravity 2.10

In passing through the retort, the carbon which is'consumed amounts to from 10% to 35% of the` raw coke introduced.

No appreciable amount of condensible material is obtained in the gas, the action being principally a very high temperature chemical. decomposition of the hydrocarbons re-l m inthe'so-called Reilly coke by which the'h 'ocarbons are cracked'to yield methane, drogen, ammonia, hydrogen sulfide and 'ot er gases. It may be said to be a cracking process which removes everything but the carbon and a small amount of ash.

The carbon resulting from the treatment am e t e rA cylinder,

above described has a gray, dull appearance, is free from volatiles and-is essentially pure carbon. l

A reduced pressure is essential to the operation of the process. The apparatus is opervacuum at the top of the retort and approximately one and one-half inches or more of vacuum at the air inlet. Such a reduced pressure apparently distributes the combustion over a large area and entirely to the center'of the charge 'ving far more satisfactory results than w en a blower is em loyed to force the air into and through t e air holes. y

The uniformit of action throughout the mass is evidence by the fact that each and every piece of treated coke presents the same exterior condition-the surface exhibitingpa dull gray appearance quite different from that of the starting material. That the process is the same throu hout the mass is evidenced by the fact t at' pieces taken from different sections of the combustion zoneare the same in all characteristics.

The calcination of the coke acts to produce a shrinkage in the pieces of the material, which shrinkage prevents bridging or stoppage of the flow of the charge downward y through the retort.

What is claimed is: 1. That method of producing carbon having a low electrical resistance, which consists in feeding coke into the upper end of a vertical retort having a relatlvely small cross sectional area; sub'ecting the coke thus fed to a temperature o approximately 17 90 C.

in aportion of the retort at a point removed from the upper end thereof; drawing air through the walls of the retort at such a point and upwardly through. the. down coming charge of coke; and gradually withdrawing, from the lower end of the retort, the carbon produced.

2. As a new article of manufacture a car- -bon suitable for lutilization as an electrode,

said carbon being characterized by being free from moisture and volatile matter, low in ash atmftresheric .pressure on the material being trea 4. That method of producing. carbon of low electrical resistance from coal tar. cokev which consists in feeding the coke in lump ated at twenty-five inches to fifty inches ofk form in a com act stream; sustaining surface combustion o said lumps in a definite zone in saidstream by feedinv air to the stream in the desired zone; an withdrawing'the products of combustion in counter-current to the entering coke stream.

5. Tha-t method of roducing carbon of low electrical resistance rom coal tar coke which consists in feeding the coke in lump form in a -compact stream; sustainin surface combustion of said lum s ina de nite lzone in said, stream by feedlng air at sub-atmospheric pressure to the stream in -thede'sired zone; and withdrawing the products of combustion in counter-current to the entering coke stream. L

6. That method of producing carbon of low electrical resistance which consists in treatingcoke, roduced as the result of the complete distil tion of coal tar, in a retort of small cross sectional area and therein subjecting the coke, as the same passes downwardly therethrough by the action of gravit to a calcining temperature approxlmatey. 1790'.J C. in the presence of a current of air and at sub-atmospheric pressure.

7. That metho of producing carbon having a low electrical resistance' which consists in treatin coke, produced as the result of lcomplete stillation of coal tar, by continuously passing the s ame, in the form of lumps,

-by gravity action through a vertical retort (.15%), having a low sulfur content (30% to .4095), having (20S-2.10) having a low electrical resistance (-.05-.07 ohms) and being distinguishable by the fact that it is easily ground.

3. That method of producing carbon of low electrical resistance whichconsists of 'ahigh specific gravity` preparing coal tar coke and thereafter passl ing said coke to, through and beyond a combustion zone, the temperature progressively rising as the coke approaches the combustion zone to approximately 1790 C.; admitting air to the combustion zone; causing said air' and gaseous products of Acombustion to ow in counter-current to the coke approaching the combustion zone; and maintaining sub-- 

